This invention relates generally to magnetic sensors of speed, direction, rotation and/or position of a member moving with respect to the sensor and, more particularly, to such sensors that are employed in instrumented bearings or bushes.
Numerous designs of bearing with built-in magnetic encoder and sensors of Hall-effect probe or magnetoresistor type are already known in the prior art.
Reference may be made for example to the following documents:
French patent applications 2 667 947, 2 669 432, 2 669 728, 2 671 633, 2 678 691, 2 678 692, 2 690 989, 2 693 272, 2 694 082, 2 702 567, 2 710 985, 2 718 499;
European patent applications 375 019, 420 040, 420 041, 438 624, 487 405, 488 853, 498 298, 518 157, 521 789, 522 933, 531 924, 557 931, 557 932, 647 851, 693 689, 701 132, 701 133, 714 029, 745 857, 751 311, 753 679, 767 385.
Reference may be made, likewise by way of example, to the following documents emanating from the applicant:
French patent applications 2 639 689, 2 640 706, 2 645 924, 2 730 283, 2 732 458, 2 717 266, 2 701 298;
European patent applications 371 835, 376 711, 394 083, 484 195, 607 719, 612 219, 619 438, 631 140, 652 438, 671 628, 725 281, 735 348.
When one wishes to ascertain both the speed of rotation of the inner race or of the outer race of the bearing and also the direction of rotation of this race, it is known practice to utilize two signals electrically out of phase by 90xc2x0 to define the direction of rotation.
Reference may be made, for example, to the documents FR-A-2 599 794, FR-A-2 660 028 and EP-A-395 783.
Other similar devices are known in the prior art for determining the angle of rotation and/or the direction of rotation of a given member with respect to several circumferentially spaced sensors.
The document WO-A-98 48 284 describes a method for detecting the direction of rotation of a wheel by means of Hall probes disposed in series in the circumferential direction of the wheel.
The document FR-A-2 750 493 describes a steering wheel angular displacement sensor comprising at least three Hall-effect cells offset by around 120xc2x0 with respect to one another.
The document EP-A-534 055 describes a rotation signaling system comprising two Hall-effect elements, a permanent magnet being arranged in such a way as to maintain a 90xc2x0 phase shift between the signals emanating from the two sensors.
Reference may likewise be made to the documents EP-A-511 459 and WO-A-92 09 138.
Also known are devices able to detect the displacement of a magnetic field source and comprising several Hall probes disposed in several assemblies placed on a predetermined locus, optionally rectilinear.
The documents WO-A-94 05 974 and WO-A-94 05 975 describe devices comprising Hall-effect elements disposed a predetermined distance apart over a predetermined locus.
The document EP-A-590 222 describes a magnetic position sensor able to detect the position of a magnetic element having a field component which vanishes at at least one point in space, this sensor comprising an array of Hall probes aligned in a direction perpendicular to said field component and to the current flowing through the probes.
Reference may likewise be made to the document EP-A-591 113.
The document WO-A-93 22 623 describes an apparatus generating a cumulative signal representing the position of a magnet with respect to a linear series of Hall-effect switches.
The known devices of the prior art for the magnetic detection, with the aid of Hall-effect probes or the like, of the speed, of the direction of rotation and/or of the position of a member moving with respect to said probe exhibit considerable bulk, are not modular and are therefore difficult to transpose from a given application to another application.
The invention relates to a sensor of position, of direction of rotation and/or of speed of a moving member, via the Hall effect or magnetoresistance, which does not have the drawbacks of the sensors known from the prior art.
To this end, and according to a first aspect, the subject of the invention is a sensor of position and/or of displacement of a moving member generating magnetic pulses, said sensor comprising a plurality of aligned sensitive elements, characterized in that the sensitive elements are divided into at least two subassemblies, the signals emanating from these subassemblies being processed by an electronic circuit able to deliver two analog signals in substantially perfect quadrature.
The sensitive elements are, for example, chosen from among the groups comprising Hall-effect probes, magnetoresistors, giant magnetoresistors and are placed equidistantly from one another.
According to a second aspect, the subject of the invention is a method of processing signals emanating from a sensor as presented hereinabove which comprises the following steps:
creation of at least two subassemblies of N sensitive elements;
summation of the signals emanating from each sensitive element of the first subassembly so as to form a first sum S1;
summation of the signals emanating from each sensitive element of the second subassembly so as to form a second sum S2;
addition of the two sums S1 and S2;
addition of the signals S1 and xe2x88x92S2.
As a variant, the even number of sensitive elements which is chosen for the creation of the subassemblies of sensitive elements is performed by programming of EEPROM, ZENER ZAPPING type, or the like.
The method can furthermore comprise amplification of the signals S1+S2 and/or S1xe2x88x92S2 so as to obtain an identical amplitude for these two signals.
According to a third aspect, a number of sensitive elements which is a multiple of four is employed to form four subassemblies of P sensitive elements, the method comprising the steps of:
summation of the signals emanating from each sensitive element of the first subassembly, so as to form a signal S1;
summation of the signals emanating from each sensitive element of the second subassembly, so as to form a signal S2;
summation of the signals emanating from the third subassembly, so as to form a signal Sxe2x80x21;
summation of the signals emanating from each sensitive element of the fourth subassembly, so as to form a signal Sxe2x80x22;
formulation of the signals S1xe2x88x92S2-(Sxe2x80x21xe2x88x92Sxe2x80x22) and S1+S2-(Sxe2x80x21+Sxe2x80x22) devoid of magnetic offset.
The method can also comprise a step of interpolation increasing the resolution of the signals emanating from the sensors.
According to a fourth aspect, the subject of the invention is a device for implementing the method as presented hereinabove, comprising an ASIC type customized integrated circuit.
According to a fifth aspect, the subject of the invention is a position and/or displacement sensor assembly as presented above, associated with a device described hereinabove, in which the sensitive elements of the sensor are incorporated within the ASIC customized integrated circuit.
According to a sixth aspect, the subject of the invention is the application of the assembly presented hereinabove to the detection of the direction of rotation of a member generating magnetic pulses, which member is of annular shape and is formed by a plurality of continuous domains having reversed direction of magnetization of a given domain with respect to the two domains which are contiguous with it.
Other subjects and advantages of the invention will become apparent in the course of the following description of an embodiment, which description will be given with reference to the appended drawings.